Add index

documentation/optimization.html

@@ -230,6 +230,7 @@ ALTER TABLE c_lp_item_view ADD INDEX idx_clpiv_c_i_v (c_id, id, view_count);
         ALTER TABLE track_e_login ADD INDEX idx_track_e_login_user_date (login_user_id, login_date);
         ALTER TABLE track_e_course_access ADD INDEX idx_teca_countconn (c_id, session_id, login_course_date);
         ALTER TABLE track_e_course_access ADD INDEX idx_c_id_session_user (c_id, session_id, user_id);
+        ALTER TABLE track_e_course_access ADD INDEX idx_session_user_login (session_id, user_id, login_course_date);
 
         ALTER TABLE extra_field_values ADD INDEX idx_efv_fv1 (field_id, value(1));
         ALTER TABLE message ADD INDEX idx_message_senddate (send_date);